It’s often said that guitar stands are a repair person’s dream. To that I would add airlines. I often get two or more broken pegheads a month. Dogs, kids, vacuum cleaners, luggage handlers, they’re all out to get your guitar.
Electric guitars, such as the Gibson Les Paul seem to be the most prone to breakage because of the peghead angle and the heavy weight. Although I see it most often in electrics, acoustics are not immune from this ailment. Most of the breaks on those seem to be due to airline damage. I just repaired a Martin “Eric Clapton” signature 000-28 from airline abuse.
Before we get into how to fix them, let’s see how first to prevent it. If you must display you guitar on a stand, make sure it’s out of reach from anything that could knock it over. Wall hangers are getting more popular (although in earthquake country where I live that could be problematic as well). Some people even have furniture cases for their prized possession. This has the added benefit of keeping the guitar humidified. The simplest way to protect your instrument is to keep it in the case! If you do travel with your guitar and can’t afford to buy it a seat, then make sure it’s in a very good case. Most hard shells are not up to the task. A Calton or similar case is the best way to go. Even then you must take precautions! Always detune your instrument and make sure the head stock is supported with a towel. This is especially true when your guitar has heavy sealed machines such as Schaller M6 or Grover Rotomatics. A careless toss by a baggage handler and snap goes the peghead.
If the peghead is cracked but the crack is not opened up, do not delay in getting it fixed. The longer you wait, the more grime and oil etc. can get into the crack and make it harder to glue. Some of these are very easy to fix. Gently pry the crack open enough to get aliphatic resin glue (Titebond, Elmer’s carpenter glue, etc.) in and clamp the break. Make sure the tuning machines are off and you use clamping cauls that will not damage the finish. Any glue residue can be cleaned off with hot water after it’s dry. If you’re not able to get glue in the crack you can use thin cyanoacrylate (super glue) as it will wick into the crack. I prefer to use aliphatic glue if I can because I believe it will bond better and if the cyano gets on the finish you will have to fix that as well. I don’t use epoxy for this (or most repairs) because it’s almost impossible to get into the crack. I also feel that it isn’t going to give you as good of a bond as aliphatic will.
I just repaired an old mandolin that had been “repaired” using a wood screw! The neck was originally two pieces with a short scarf joint joining the headstock to the neck shaft. The hide glue had failed and the first fix was to use more hide glue and a wood screw. Unless you’re installing a strap button at the heel or installing tuning machines, screws have no place in guitar repair. I can’t tell you how many times I’ve seen this kind of “fix” and they never work for long. This goes for putting a wood screw in the heel of a neck to re-attach that.
These repairs can be problematic. The short scarf joint is not sufficient in itself to hold the neck together so another method has to be used. On the mandolin I cleaned up the glue joint so the new glue would stick to the wood and after aligning the two pieces, glued it up. After waiting a day, I used a router to make a cut in the neck between the headstock and the shaft 3/8″ wide and about that deep. I’ve tried elaborate jigs to accomplish this and have determined it’s easier just to clamp the neck in and freehand the router. I then clean the channel with a sharp chisel and make a piece out of Eastern hard rock maple to tightly fit the channel. After this is glued in and dry, the maple is shaped to the profile of the neck. I’ve found this spline works very well.
The next problem is to fix any finish that was chipped or cracked during the break. If it’s a transparent color such as a cherry red or amber this can take a while to get right and sometimes may never be invisible. If it’s a sunburst finish you can simply take the darkest color and move it down a bit to cover the crack.
I recently repaired a Gibson ES-335 that required nothing more that gluing. The crack was fresh and no finish work was needed to make the repair invisible. Only experience will give you the tools to make an estimate of the cost.